Process of degumming silk



Patented Feb. 7, 1933 UNITED STATES PATENT OFFICE LATIMER n. mum's arm LOU A. srnenunima, or cmcmnarr, onro, assrenon we ran TWITOHELL raocnss COMPANY, or CINCINNATI, cure, a coaroaa'rrou or 01110 PROCESS OF DEGUMMING SILK Ho Drawing.

This invention relates to a process of treating raw silk to remove from it the natural gum. Genuine silk is produced by the silkworm (Bombg a: more), and comprises the fiber which is known as fibroin, and the yellow gum sericin which is about to 30% of the weight of the silk fiber.

This sericin coats the silk ,fibers and imparts to the silk a harsh, stiif feeling and also interferes very materially with the dyeing of the silk- It is therefore necessary to remove the sericin from the silk, which process is usually called degumming, discharging or stripping. I

It is generally preferred to practice this process after the silk has been woven into cloth or fabric, though it may be carried on if desired beforehand. The removal of the water and 250 lbs. of olive oil, red oil or,

other low titer soap. The temperature of the bath is held just below the boiling point, say 205 F. After two hours, the silk is removed from the first bath and treated for approximately twenty minutes in a second bath containing 2500 gal. of water and 50 lbs. of soap. The original degumming bath may be used to degum two additional 350 lb.

' batches ofsilk by adding seventy-five lbs.

of soap before each boil. After three boils the bath becomes heavily charged with sericin ,and is either discarded or used in the Oll sulp dye house under the name of boiled liquor.

There are many disadvantages of this rocess, however, the first of which is the 'gh consumption of relatively expensive fatty acid soap. Second, the time of the treatment is excessive and the amount of heat required for the long treatment is an undesirable economic factor. Third, a scum is left on the surface of the bath and adheres to the silk as it is withdrawn, and if not completely removed by a second bath, causes Application filed March 16, 1929. Serial No. 347,729.

irregularities in later dye operations. Fourth, it is difficult to wash all of the fatty acid soap from the silk without injuring it physical and the portions or traces of the fatty acid soap left in the silk are decomposed in the acid dye-bath to fatty acids which are insoluble and cause uneven dyeing of the fabric.

The object of this invention, therefore,

is to provide a process of degumming silk which is free from the disadvantages outlined in the previous paragraph.

Another object of this invention is to provide a material or reagent adapted to wash or remove the sericin from silk.

This invention comprises treating the natural silk alone or associated with other fibers or materials with an aqueous alkaline solution and an aqueous solution of a powerful emulsifying agent which removes the natural gum and also any oil or other similar material which may have been deposited upon the fibers during some previous treatment. This emulsifying agent is so powerful that it prevents the formation of any scum upon the surface of the bath in which the silk fiber is treated. It is likewise the concept of the inventors to use an emulsifying agent which is safety in the presence of the preferred emulsifying agent of this invention.

This preferred reagent comprises mineral onates, recovered as by-products in the practice of the Petroflf-Humphre process of refining mineral oil such as lurioating stock into white oil and the light colored technical oils. This process is exemplified by the following patents:

Petrofl" Humphrey 1,286,179 November 26,1918

1,087,888 February 19,1914

Mineral oil sulphonates fall in'two' gener a1 classes. The mahogany sulphonates or oil phonates for degumming silk because they are more power 111 as emulsifiers than the sludge layer sulphonates, and also because they have less tendency to discolor the silk.

These sulphonates are most available in the form of sodium salts, though other water soluble salts may be used.

Our investigation has determined that in the presence of the maho any sulphonate it is possible to carry the a ali content of the degumming solution to as high as .03% sodium hydroxide without injuring the silk fiber. The general range of alkalinity recommended is, therefore, between .01 and .03% sodium hydroxide solutions. Other alkalies or potential alkalies may be used instead of the sodium hydroxide, the quantities being adjusted to provide equivalent alkalinity. The amount of mahogany sulphonates used is less critical but the use of a .5 to 1% aqueous solution (based on. weights) is recommended. The silk is preferably immersed in this aqueous solution containing .03% sodium hydroxide and .5 to 1% mahogany sulphonate at a temperature slightly below boilmg for a period of between 10 and 45 minutes. The surface of the degumming bath is entirely free from scum due to the unusual emulsifying powers of the mahogany sulphonate. One bath, with replacement of the alkali I whichhas been used ment, ma be used for at least four batches of silk be ore the concentration of sericin becomes harmfully high. This result is possible 40 because of the unusual colloidal power of the mahogany sulphonates to disperse the sericin which has been saponified by the alkali. Since the, alkali is used up by each treatment, thedegummed silk fiber is not injured by the solution.

Before being placed in the dye bath the silk is rinsed in water butshould any of the .mahogan sulphonate remain on the silk no harm is one since the acid dye bath converts the mahogany soap to mahogany acid which is also readily soluble. The silk so degummed, therefore, dyes evenly, first, because it has not been contaminated with any scum, and secondly, because traces of'the emulsifier are soluble in the dye bath.

For example, a bath is made up as follows:

10,600 parts 1200 gahH O 1100 parts= 100 lbs. Na'mahogany sulf phonates 411bsiNaOH These quantitiesprovi'de a recess wherein the sericin is saponified an completely removed fromjthe-silk fiber. and the alkali con'; tent of the treatment bath simultaneously up in previous treatsubstantially exhausted so that after the silk fiber is exposed, the solution is not of sufiicient strength to be injurious to it. This bath will degum 150 lbs. of silk fabric within thirty minutes and without injury to the silk.

From this example it will be observed that the preferred reagent comprises substantially 100 parts maho any sulphonates to 3 parts sodium hydroxi e by weight.

A substantial problem resides, however, in constituting an entirely homogeneous reagent of mahogany sulphonates and alkali, that is, a reagent in which the alkali will not settle or separate from the sulphonates, so that some portion of the particular batch contains a' greater percentage of alkali than some other portion. Moreover, the mahogany sulphonates alone are quite viscous and gummy and consequently hard to pour, handle, and measure-with accuracy.

If water is added in (an eflort to thin down the material the alkali salts out the mahogany sulphonates or a portion of the mahogany sulphonates. If, however, a water soluble solvent, such as-methyl alcohol, is added to the mahogany sulphonates and alkali an entirely homogeneous body is formed in which the components do not salt out or separate. For instance, asatisfactory reagent is constituted as follows:

3 parts sodium hydroxide 110 parts sodium mahogany sulphonates containing 10% water 8 parts 95% methyl alcohol.

If desired, oil may be added to this mixture to further reduce the viscosity and to increase the solubility of the substance without causing a separation of the alkali. Other- 105 wise expressed, we add to the mahogany sulphonates andalkali a mutual solvent for the alkali and sulphonates such as an aqueous alcohol or the like, and this efiects' a homogeneous admixture of the mahogany. sul- 110 phonates and alkali, so that all portions of a given batch contain substantially the same percentage of components. I

Having described our invention, we desire to be limited only by the ensuing claims:

1. A material adapted to degum silk, said material comprising mineral oil sulphonates, an alkali, and a liquid in which the sulphonates and alkali are both soluble. v

2. A material adapted to degum silk, said 120 material comprising, mineral oil sulphonates, an alkali, and alcohol. a

3. A homogeneous material adapted to degum silk,'said material comprising substan- .tially 110 parts mahogany sulphonates con- 125 taimn about 10% water, 3 parts sodium hydroxi' e, and 8 arts 95% methyl alcohol.

- '4. The art 0 effecting a substantially comlete removal of sericin from silk without inqury to the silk, said art-comprising, subject-130 ing the silk bearing the sericin simultaneously to the chemical and colloidal action of a hot aqueous solution, the chemical action being provided by an alkali in said solution equal in strength to between .01 and 03% sodium hydroxide, the colloidal action being provided by water soluble salts of mahogany sulphonic acids adapted to disperse the sericin saponified by the alkali throughout the solution Without scum formation.

5. The art of efiecting a substantially complete removal of sericin from silk without injury to the silk, said art comprising, subjecting the silk bearing the sericin simultaneously to the chemical and colloidal action of a hot aqueous solution, the chemical action being provided by an alkali in said solution equal in strength to between .01 and 03% sodium hydroxide, the colloidal action being provided by water soluble salts of mahogany sulphonicacids adapted to disperse the sericin saponified by the alkali throughout the solution without scum formation, the quantity of the treating solution being so adjusted to the quantity of silk treated that the available alkali content of the solution is substantially reduced by the saponification of the sericin on the silk so that the treating solution is not injurious to the silk fiber as it becomes exposed by removal of the sericin.

6. The method of degumming successive batches of silk in a single treating bath, said method, comprising, alkalinizing the treatment bath before each batch of silk is introduced, the quantity of alkali introduced being related to the quantity of sericin to be saponified by its action so that the available alkali in the bath is substantially reduced by its action on the sericin, maintaining the removed sericin in a dispersed condition throughout the bath without scum formation by virtue sulphonic acids, the process being carried out our names.

LATIMER D. MYERS. LOU A. STEGEMEYER.

of the presence in the treating bath of water soluble salts of mahogany sulphonic acids, and replacing alkali after each bath in relation to the next succeeding batch of silk to be degummed.

7. The art of eifecting a substantially complete removal of sericin from silk without injury to the silk, said art comprising, subjecting the silk bearing the sericin simultaneously to chemical and colloidal action of a hot aqueous solution, chemical action being provided by an alkali adapted to saponify the sericin present on the silk being treated, colloidal action being provided by water soluble salts of mahogany sulphonic acids adapted to emulsify the saponified sericin.

8. The art of effecting a substantially complete removalof sericin from silk without injury to the silk, said artcomprising, subjecting the silk bearing the sericin simultaneously to a chemical action and a colloidal action in a hot aqueous solution, the chemical action being providedby an alkali and the colloidal action by water soluble salts o mahogany 

